Warning alarm on 2002 X-star

Was out on Saturday in my 2002 X-star. After about 2-3 hours on the water, I was just idling waiting for a rider to get his board back on after a fall. A steady warning beep started going off. Oil press, engine temp, voltage all looked normal. The boat was running normal. I shut the boat off, took a peek in the trunk and no obvious sign of problems. Once earlier in the season I didn't have the impeller cover tight after changing the impeller and some water was spraying out and somehow that sent the alarm off. Thought maybe that was happening again, but it wasn't. I had my friend start the boat while I had the trunk open and everything seemed normal and the alarm was off. We boarded without any problems for another 2 hours without problem closely watching the gauges and listening to the engine. When I loaded the boat, I was waiting for the 3 boats in front of me and I was idling for about 5-10 minutes slowly and the boat just died. I turned it over and it started right back up, but it has never died at idle like that before on me, and I've put almost 100 hours on it this summer. Any ideas. I'm concerned about taking it out again before I figure out why the alarm was going off?